(So named (Latin rubidus, "red") by its discoverers, from the red lines in its spectrum) A soft, silvery-white, very reactive, metallic chemical element, one of the alkali metals, that ignites spontaneously in air and reacts violently with water. It occurs in the minerals pollucite, carnallite, leucite, and lepidolite, from which it is obtained commercially. It is used as a catalyst, in photoelectric cells, in cathode-ray tubes, and in filaments of vacuum tubes. Similar to potassium in its chemical properties, one of rubidium's natural isotopes is radioactive and could be used to locate tumors.
Rubidium was discovered spectroscopically in 1861 in Heidelberg, Germany by Robert Wilhelm Bunsen and Gustav Kirchhoff as an impurity in samples of the mineral lepidolite.
Symbol: Rb
Atomic number: 37
Atomic weight: 85.4678
Density (at
room temperature and
pressure): 1.532
g/
cc
Melting point: 39.31°
C
Boiling point: 688°
C
Main
valences: +1
Ground state electron configuration: [
Kr]5s
1
See also: rubidium-strontium dating